[From Bill Powers (961128.2200 MST)]
Bruce Abbott (961127.2010 EST)
Unless I just _changed_ my posture, it is not relevant, not an act.
Tracy Harms (1996;11,27.19:12 MST)
This looks very wrong to me. There are perceptions being actively
controlled by a given posture even when that posture goes unchanged. Every
posture is the result of a combination of muscular tensions, and the nature
of muscles means that there are error-corrections which alter these muscle
tensions over time as a given posture is held *unchanged*.
This is a very important point. Tracy is right. When a control system is
actively controlling, it may not be doing anything that an external observer
can see as an "event." But it is actively controlling; the slightest
disturbance will result in opposition, the slightest change in the reference
signal will produce a corresponding change in the controlled variable. A
controlled variable doesn't actually have to vary to be either controlled or
a variable. The output of the control system is ALWAYS having consequences,
even when it's constant. The same control system, turned off, may exhibit
exactly the same observed absence of behavior, but it is not controlling.
Bruce says
I agree completely that we are actively controlling perceptions all the
time, just as you (and PCT) describe. But it is the consequences of
movements that I want the model to focus on -- the dynamic changes in the
values of these movement-related perceptions.
This forces the discussion back to the level of events instead of continuous
relationships. Remember my discussion of the lever. The position of the far
end of the lever is always related to the position of the near end by the
constant of proportionality. The position of the far end is ALWAYS a
consequence of the position of the near end, even when both ends are
stationary. You can create the picture of one event causing another event
simply by moving the near end in a way that you perceive as an event -- for
example, a quick wiggle up and down. This event will have the consequence
that the far end will move in a quick wiggle down and then up. But that has
nothing to do with the actual input-output relationship. The "eventness" of
this observation is simply an artifact of the way the independent variable
is "moved." A "movement" is simply a change in position seen as an event.
All during a movement of one end of the lever, the position of the other end
remains in the same relation to the end that is manipulated. It is this
continuous relationship that explains how input and output variables are
related -- not the particular way in which the input variable may change (or
not change).
When I took graduate courses in a Spencean department, it was emphasized
over and over that you had to set up experiments in a way that allowed
definite events to be observed. In a maze-running experiment, for example,
you can't just put the rat into the starting chamber and let it go. The rat
moves around in a continuous way, eventually becoming oriented and starting
to move up the alley. But this doesn't give you any definite moment to call
the "start" of the run. What you need to do is to use a photocell or a
swinging barrier that records the start as a relay or switch closure; this
gives you an event that occurs at a specific moment in time. Then you have
something to measure. The same goes for the end of the run; again you need a
relay or switch closure to create a specific event marking the end. Once you
have reduced behavior to events, you can count them, calculate their
probability of occurrance, measure the elapsed time between them, and
measure their frequency.
This requirement reflects the observer's assumption that environmental
events cause behavioral events. This is how Skinner thought of
"consequences." A consequence is an event produce by a preceding series of
behavioral events, marked by contact closures. The probability of a contact
closure can be related to the frequency of contact closures, and the theory
of behavior can be stated in terms of events and their effects on
probabilities or frequencies of events.
I think it's interesting and significant that in physics, events per se are
not considered causal. If you drop a steel ball on a steel plate, the
velocity of the ball reverses at the moment of contact, creating an event we
call an "elastic collision" or a "bounce." But it is not the "bounce" that
causes "reversal" of the velocity; that is just a convenient way to refer to
the observation in human terms. What causes the bounce is an episode of
elastic compression of the ball and the steel plate, which decelerates the
ball to a stop and then, as the compression continues to react against the
ball, accelerates the ball upward, while various momenta are conserved. The
event really consists of a series of ongoing smooth interactions that begin
imperceptibly as the fields surrounding the atoms of the ball approach the
fields surrounding the atoms of the steel plate, go through continuous
smooth changes, and finally die out again imperceptibly as the fields
separate again. The "eventness" of this interaction through time is entirely
in the eye of the beholder, because human beings (for whatever reasons) find
it convenient and natural to perceive in terms of events. And it is clearly
not the "eventness" that is causing the phenomenon; just the opposite. The
underlying continuous interactions through space and time --plus the
properties of human perceptions -- are what create the subjective
impressions of events.
This picture becomes confused when we take an animal that behaves
essentially continuously and put it into a situation where the _environment_
is set up to create events. As the rat approaches the bar, its body and paws
are moving smoothly and continuously through various patterns of change. It
noses around the bar and rears up, all in a continuous flow of movement. At
some point, the weight of the rat depresses the bar far enough to cause a
microswitch to snap from open to closed. At that instant, an "event" is
recorded. What the rat was doing immediately before and immediately after
this event is NOT recorded, except by the video camera if the experimenter
has provided one. As far as the data are concerned, everything that the rat
did was done at the instant that the microswitch snapped closed; before and
after that instant, the rat was doing nothing.
The apparatus, of course, is set up so that the input events are counted or
timed, and when a certain criterion is met, the output event is triggered; a
pellet drops suddenly into a food dish. At this moment, a "reinforcer" is
said to have been administered. The apparatus is set up to conform to the
experimenter's idea that natural phenomena occur as discrete events. The
events seems discrete, that is, on the scale of normal human perception.
They are all actually continuous processes, although they may happen more
rapidly than we can follow.
Now consider this reinforcing event from the standpoint of the rat's
continuous sensory experience of the world. The rat's nose and eyes are
always providing it with a picture of the world; as the rat moves around
this picture continuously changes. As the rat's nose passes close to the
food dish, the smell of the food in the magazine, and the flakes of food
adhering to the surface of the cup, becomes stronger. The rat zeros in on
this smell, but tasting and seeing no food there passes on to other
activities. Its world is full of continuously waxing and waning scents;
whiffs of air containing moisture, the smells of previous occupants of the
cage, smells of traces of urine and feces both its own and from others of
its species who have been in the cage. It sees the items in the cage; glints
of light, dark places, and so on -- who knows what a rat sees?
Into this continuously changing world of perception there comes a sudden
change: a piece of food falls into the cup, rattles and bounces for a time
that seems short to a human but probably seems longer to a rat, with its
short-coupled nervous system. The smell of food intensifies and the rat sees
the food in the cup. It moves itself to the cup, rearing up, twisting its
head to get its mouth into the cup, bringing its forepaws into play to seize
the food and move it from the cup into its mouth. It salivates and chews,
intensifying the tastes and smells of the food, and passing the food inward
to its stomach. While it's doing this, it may be balancing on its
hindquarters and turning the piece of food with its paws as it nibbles, or
it may move back to the lever to continue its explorations until another
contact closure takes place, chewing on the previous piece of food all the
while. It may move back to the cup, but have to wait until it has finished
chewing and swallowing the previous piece of food before it has room to
stuff the new one into its mouth.
At the moment that the food is released to fall into the cup, a
"reinforcement" is recorded. Everything that happens to the rat, data-wise,
is compressed into this brief moment. Nothing the rat was sensing in any
modality before or after this event is recorded.
So what we end up with is a data set consisting of instantaneous events
occuring at specific instants of time, with no record of all the continuous
processes of action and (inferred) perception that were going on between the
events.
If rats can indeed perceive and control in terms of events, defined as we
perceive them, then experiments like these might tell us something about how
they do this. But if they can't (or if they are nowhere near as good at this
as we may think), then we can still read event-based phenomena into the
results simply because we have forced the environment to work in terms of
discrete events rather than continuous variations.
In order to resolve this problem, the first thing we have to do is to
recognize events not as natural units of physical phenomena, but as modes of
perception. As long as we think that events are natural units, we will fail
to see that we are making a specific hypothesis about what the rats perceive
and what their internal mode of operation is. To recognize this we have to
see first how we ourselves impose eventness on an otherwise continuous world
of experience.
Best,
Bill P.